At the time of compression processing for video data in an image-sensing apparatus such as a digital camera or digital video camera, compression processing at a target bit rate (the amount of codes) as a base needs to be performed. At the same time, however, there is demand for efficient compression of data into a limited amount of codes with fine perceived resolution.
To meet the demand, Japanese Patent Laid-Open No. 2000-134622 (D1) proposes dividing an input image into regions, categorizing each region as a region of interest or a region of non-interest, and encoding the image while allocating a larger amount of codes to a region of interest than to a region of non-interest (encoding the region of interest at a higher bit rate), at the time of image compression. Note that in D1, each region is categorized as a region of interest or a region of non-interest based on region-of-interest information accompanying an input image and the luminance distribution in each divided block.
However, in the method described in D1, an input image is divided into regions, and each region is categorized as a region of interest or a region of non-interest, at the time of image compression. For this reason, there is no difference in signal processing before image compression between a region of interest and a region of non-interest. Examples of such signal processing before image compression include camera signal processes such as noise reduction processing for a signal output from an image-sensing device such as a CCD and aperture correction.
In other words, a signal to be subjected to compression encoding has undergone the same set of camera signal processes, regardless of whether the signal belongs to a region of interest or a region of non-interest. For this reason, a realizable image-quality improvement effect may not be obtained even if a larger amount of codes are allocated to each region of interest at the time of encoding.